1. Field of the Invention
The invention relates to dispensers of fluid dispersions.
2. Brief Description of Related Art
A wide variety of fluid dispensers are known and commercially available to dispense metered proportions of a contained fluid from containers. For example, U.S. Pat. No. 3,749,290 describes a trigger actuated dispensing pump assembled with a fluid container. Upon actuation, a measured proportion of the contained fluid is dispensed from the containers.
Of particular importance as fluid dispensers are metered dose inhalers (MDI) employed to administer fluid medications to animals, including humans.
The use of inhalers is well known and the art has developed over the past twenty five years to cover many versions of the basic concept of a "pumping" type medication applicator. The device may be manually pumped (such as described in U.S. Pat. No. 5,284,132) or a pumping like cycle may be utilized. The medication may also be repeatedly released from a pressurized disposable canister to create repeated sprays or inhalations as needed.
Representative of the early inhalers for oral and intra-nasal administration of medications are those described in, for example, U.S. Pat. Nos. 3,361,306; 3,183,907; 3,565,070; 4,206,758; 4,803,978; 4,934,358; 4,955,371; 5,060,643; and 5,351,683. Representative of nasal-pharyngeal inhalers for large mammals such as a horse is that described in U.S. Pat. No. 5,062,423.
Metered dose inhalers (MDIs) are, at present, the most efficient and best-accepted means for accurately delivering medications in small doses to an animal's respiratory tract. Therapeutic agents commonly delivered by the inhalation route include bronchodilators (B.sub.2 agonists and anticholinergics) corticosteroids, and anti-allergics. Inhalation may also be a viable route for anti-infective, vaccinating, systemically acting and diagnostic agents, as well as anti-leukotrienes, anti-proteases and the like.
MDIs are available in several types. Most frequently, MDIs comprise a pressure resistant container (canister) typically filled under super-atmospheric pressures with a product such as a drug dissolved in a liquefied propellant, or micronized particles suspended in a liquefied propellant. The container is fitted with a metering valve. The valve is movable from an inner (charging) position to an outer (discharging) position. A spring bias holds the valve in the charged position until forced to the discharge position. Actuation of the metering valve allows a metered portion of the canister content to be released, whereby the pressure of the liquefied propellant carries the dissolved or micronized drug particles out of the container and to the patient. A valve actuator also functions to direct the aerosol as a spray into the patient's oropharynx.
Surfactants are usually dissolved in the aerosol formulation and can serve the dual functions of
lubricating the valve and reducing aggregation of micronized particles.
Representative of pharmaceutical formulations for use in metered dose inhalers are those described in U.S. Pat. No. 5,190,029. The MDI devices for administering such pharmaceutical formulations are also well known as seen for example in the descriptions given in U.S. Pat. Nos. 3,361,306; 3,565,070; and 4,955,371 which are incorporated herein by reference thereto.
A disadvantage arising from use of the known devices is that the patient cannot control the uniform dispersion of medicament in the aerosol container at any given time. The containers are generally not transparent to view, being light protective of the contents. Shaking them is not always practical to assure homogeneous, uniform dispersion of solid particles in the liquid carrier. Generally, homogeneous dispersions of medications tend to separate in about 20 seconds due to the effect of gravity.
The modification of a conventional metered dose inhaler by the method of the present invention obviates this disadvantage in that the aerosol formulation, particularly where the medication is a solid to be dispersed in a liquid carrier, is mixed to homogeneity immediately prior to charging of the metering valve for subsequent release.